(1) Field of the Invention
The present invention relates to a locking mechanism for a table leg. In particular, the present invention relates to a mechanism for locking a table leg in an extended, use position, and in a folded position when it is desired to store the table or otherwise not use the table. The locking mechanism is secured to the underside of the table and preferably, there are at least two locking mechanisms per table, one located adjacent each end of the table.
The locking mechanism is comprised of a bar, which supports a table leg. The bar is pivotally mounted between extension portions of mating right and left flanges on a pivot bar axis, off center from the longitudinal axis of the bar. The flanges form a mounting bracket and serve to secure the mechanism to the table. To lock the bar in the extended, use position, a locking rod portion of a first locking member, which is connected to a lever, is seated in a locking channel formed on one side of the bar, spaced from the bar pivot axis and opposite a lever pivot axis. Releasing the locking rod from the channel, by moving the lever to a release position, enables the bar and table leg to pivot into the folded position. The lever serves to lock the bar in the extended position when the axis around which the connection between the first locking member and the lever rotate is moved to a position overcenter a plane connecting through the axis of the locking rod and the lever pivot axis. The locking rod is also adjustably connected to the lever so that the tension of the rod seated in the locking channel can be regulated. This ensures that the rod will always apply a sufficient force against the bar to lock the bar in the extended position.
When the lever is released, the lever moves past the overcenter position which enables the rod to move out of the locking channel. This permits the bar to pivot into the folded position. In the folded position, a second locking member engages an extension portion of the bar to block the bar from moving back into the extended position. A handle portion is used to move the second locking member away from the bar extension so that the bar is again able to be moved back into the extended position. The bar is also provided with a guideway that permits the table leg to be laterally adjusted along the length of the bar for positioning the table leg away from floor obstacles such as floor registers, electrical outlets, uneven carpeting and the like. This helps to keep the table level.
(2) Prior Art
The prior art has described various locking mechanisms that enable a table leg to be unlocked from a folded position and then moved into and locked in an extended, use position. One of these is my U.S. Pat. No 4,838,181 which describes a table leg coupling assembly that is comprised of a pivotally mounted bar having first and second recess, offset 90.degree. from each other. A spring biased lever has a locking dog that seats in the recesses to lock the bar in either the extended or the folded position, corresponding to the first and second recesses. However, this locking mechanism is not provided with an adjusting means for regulating the tension of the locking dog in the bar recesses. As the spring controlling the locking dog loses some of its resiliency, the locking dog may have a tendency to release from the recesses. In the use position, this could cause the table to collapse, resulting in property damage as well as personal injury. It should be noted that the pivotable bar in this patent is also provided with an elongate guideway that enables the table leg to be positioned laterally along the length of the bar. This serves to position the table leg away from floor obstacles and uneven floor contours to help ensure that the table remains level while in the use position.
Another locking mechanism for a table leg is shown in U.S. Pat. No. 3,528,377 to DeSaussure. This patent describes a table leg that is locked in the extended position by the nose of a latching member which snaps into a slot provided in the table leg. U.S. Pat. No. 3,554,141 to Burr shows a table leg that is locked in the extended position by a cross bar that seats in a J-shaped groove portion of a plate connected to the table leg. U.S. Pat. No. 3,845,728 to Piretti describes a folding table leg having a releasable locking device comprising a lever arm having a hook portion that engages a similarly shaped end plate at the upper end of the table leg. U.S. Pat. No. 4,573,415 to Ramey describes a locking device where a rod blocks an extending tab portion of a plate forming a portion of a bracket that supports the table leg. U.S. Pat. No. 4,561,622 to Heinzel is less related to the present invention and describes a locking mechanism having a lever that cams against opposed cam surfaces on a locking cam plate to hold the table leg in the folded and the extended positions.
What is not shown by the prior art but is needed is a locking mechanism for a table leg that uses an overcenter locking lever connected to a locking member to lock the table leg in the extended position. That way, the locking mechanism is prevented from releasing out of the locked position unless the lever is manually moved out of the overcenter, locked position. The locking mechanism of the present invention fulfills this need and is comprised of a locking rod that seats in a locking channel of a pivotable bar to lock the bar in the extended, use position. The pivotable bar supports the table leg. The locking rod is connected to a lever that is moved to an overcenter position to lock the locking mechanism and is moved to a release position to release the locking rod from the locking channel. This enables the bar to pivot into the folded position. The locking rod is also adjustably connected to the lever so that the locking tension of the rod seated in the locking channel can be regulated. Thus, as the components forming the locking mechanism wear through use, the locking tension between the locking rod and the bar can be maintained at a sufficient force to ensure that when the pivotable bar is locked in the extended position, the locking mechanism is able to withstand a significant amount of loading and lateral forces without releasing from the extended position. Also, forming the pivotable bar with a guideway enables the table leg to be moved laterally along the length of the bar. This provides for moving the table leg away from floor obstructions and ensures that the table can be supported in a level position.